1. Field of the Invention
Embodiments of this invention are related to packet processing devices.
2. Background Art
Ethernet, which was initially a local area network (LAN) technology in relatively small geographic areas, has evolved to become the default data link layer (i.e. layer 2 of the Open System Interconnection (OSI) protocol model) protocol for data transport. Over time, Ethernet was extended beyond the customer LAN across provider (carrier) networks. As Ethernet evolved as a carrier grade technology, accompanying operations, administration and maintenance (OAM) frameworks have been developed to support aspects such as high levels of resiliency and ease of deployment. Several standards, including IEEE 802.1ag have been adopted by equipment manufacturers, carriers, and service providers.
IEEE 802.1ag Ethernet Connectivity Fault Management (CFM) is an OAM standard used to perform fault detection, isolation, and verification on virtual bridge LANs. It defines protocols and practices for OAM for paths through 802.3 bridges and local area networks (LANs). For example, CFM defines protocols to manage geographically-dispersed customer networks that are interconnected through provider bridged networks.
IEEE 802.1ag standard defines maintenance domains (MD), maintenance associations (MA), maintenance end points (MEP), and maintenance intermediate points (MIP). MDs are management spaces in a network, typically owned and operated by a single entity. Example MDs are operator domain, provider domain, and customer domain. Each maintenance domain is assigned a unique level number ranging from 0 to 7.
MEP is a point at the edge of the MD, and defines the boundary for the MD. CFM operates at the connectivity layer of OAM monitoring paths between non-adjacent devices in an MD. A MEP sends and receives CFM frames through the relay function, drops all CFM frames of its level or lower that come from the wire side. A MIP is a point internal to a domain, not at the boundary. CFM frames received from MEPs and other MIPs are cataloged and forwarded, all CFM frames at a lower level are stopped and dropped. An MA is a set of MEPs, all of which are configured with the same MAID (Maintenance Association Identifier) and MD Level. FIG. 1 illustrates the Ethernet OAM domains and levels.
FIG. 1 illustrates a network layout 100 between customer networks 101 and 103. A router 102 in customer network 101 and a router 104 in customer network 103 are in a MA in a customer level MD. Routers 102 and 104 are each an MEP at the customer level. Routers 102 and 104 are coupled to routers 106 and 108, respectively, of operator networks 105 and 107. Operator networks 105 and 107 are coupled through core network 111 by routers 110 and 112, facilitating the end-to-end connection from 102 to 104.
In order to facilitate connecting geographically dispersed customer networks 101 and 103 which are Ethernet networks, the provider may implement a technology such as, but not limited to, Multiprotocol Label Switching (MPLS)/Internet Protocol (IP) or Virtual Private LAN Service (VPLS) which encapsulate the customer Ethernet packets over the provider networks. This encapsulating network may extend from the edge of one customer network to another (e.g. operator-facing edge of network 101 to the operator-facing edge of network 103).
Based upon this network layout, a provider level MD extends from the customer-side interface of router 106. The outer (e.g. customer network facing) interfaces of routers 106 and 108 are each an MEP at the provider level. Operator level MDs are between non-provider interfaces of the router pair 106-110 and 108-112. Customer level MIPs can be located in customer-network facing interfaces of routers 106 and 108. Provider level MIPs can be located in core network facing interfaces of routers 110 and 112, and operator level MIPs can be located in operator network facing interfaces of routers 106, 108, 110, and 112.
FIG. 2 illustrates a network 200 having network devices (e.g. routers, bridges, switches, hubs) A 202, B 204, C 206, D 208, and E 210. Routers A 202 and E 210 have MEPs at the same level belonging to the same MA. When network 200 is fully operational, the MEP in A 202 may communicate with the MEP in E 210 by transmitting OAM packets out of A 202 through the interface coupled to D 208, and then packet is forwarded by D 208 to destination MEP at E 210. Messages such as keep alive messages (also referred to as Continuity Check Messages or CCM), may be sent from the customer level MEP at A 202 to destination MEP at E 210. OAM messages such as CCM may be locally generated by an OAM client.
If the path A-D-E fails, for example, because D 208 has failed, the data traffic other than OAM traffic between A and E may continue by transiting through a new route such as through B 204 and C 206. The data traffic other than OAM traffic, which can be referred to as “routed traffic” relatively quickly adapts to a new route to E 210 because a routing protocol (e.g. Border Gateway Protocol (BGP), Open Shortest Path First (OSPF)) would update the routing table (also referred to herein as “forwarding table”) at A 202, where the routed packets rely upon the routing table in order to determine the interface through which to exit the router (i.e. “egress interface”).
OAM packets which are locally generated, however, are injected into an egress packet processing pipeline below the network layer and rely upon an MEP database to determine the egress interface. The MEP database is a database dedicated for OAM use. The MEP database is updated based upon received CCM that are received on an interface.
Because these locally generated OAM packets rely upon the MEP database to determine the egress interface, and because the MEP database may not be updated as quickly as the routing table, the OAM packets may continue to use the failed route to the destination MEP (e.g. E 210) and incorrectly report failure of the destination MEP as well as fail to protect the actual path (in this case, the new path through B 204 and C 206 to E 210) through which the routed traffic reached E 210.